Keep Parcel size stable.

The size of 32-bit on arm 'Parcel' was accidentally changed. Fix this by
making stability 16-bits (there is not enough space in Parcel right now
to keep the 32-bit mask without combining some of the bools). This broke
a device in internal master with some 32-bit prebuilts.

Bug: 137348710
Test: TH
Test: boots on broken device
Merged-In: Ifd9aa07ae359557ff94b600c1b64bb565be85dc2
Change-Id: Ifd9aa07ae359557ff94b600c1b64bb565be85dc2